Effects of elevated temperature on growth, respiratory-deficient mutation, respiratory activity, and ethanol production in yeast

Abstract

Some mesophilic yeasts and a thermotolerant strain of Saccharomyces cerevisiae were found to grow at 40 °C in complex media containing 1% yeast extract when an inoculum of 106 or more cells∙mL−1 was used. Yeast extract (6%) permitted Saccharomyces cerevisiae to grow at 40 °C even with a smaller inoculum size (105 cells∙mL−1). The fraction of respiratory-deficient (petite) mutants in 40 °C grown culture was less than 10% except for the thermotolerant strain, which showed greatly increased levels depending on culture conditions. Seven of eight yeast strains exhibited extremely reduced cytochrome oxidase activity when grown at 40 °C irrespective of the frequency of the petite mutation. In contrast, the accumulation of ethanol in the medium and the ethanol-producing activity of the cells were not affected by growth at 40 °C.